The present invention relates to a finisher for a copier, printer or similar image forming apparatus and, more particularly, to a finisher operatively connected to the paper outlet of the image forming apparatus for binding papers sequentially driven thereoutof.
A finisher for the above application is often implemented with a binder capable of binding papers sequentially distributed from an image forming apparatus to bins and positioned on the bins in neat stacks. This type of finisher has a chuck for chucking a paper stack with a pair of chucking members and then bringing it to the binder. The binder has a binding mechanism arranged perpendicularly to an intended direction of paper discharge. Hence, the chuck is so constructed as to move the paper stack to the binder perpendicularly to the direction of paper discharge. At this instant, the paper stack is prevented from rotating due to gravity in the direction of paper discharge, since it is moved along the rear edge of the bin. To cause the binder to perform both of rotation and parallel movement, the finisher may be provided with two drive sections respectively assigned to a rotation section and a parallel movement section, or may be provided with a drive source on a movable portion thereof. To stop the movable portion :at particular positions, use may be made of sensors.
However, the conventional finished has some problems left unsolved, as follows. When the chuck chucks a paper stack and moves it in the direction parallel to the intended direction of paper discharge, a guide provided at the rear edge of the bin has to be retracted. Then, a support bearing the force ascribable to the weight of the paper stack is lost. In this condition, it is likely that the paper stack held by the chuck is rotated about the chucked portion thereof due to gravity and, therefore, bound defectively. When independent drive sources are respectively assigned to the rotation section and the parallel movement section, as mentioned above, complicated control over the drive sources is necessary for the two kinds of motions to be interlocked. In addition, such drive sources result in a complicated mechanism and an expensive finisher. On the other hand, when a drive source is mounted on a movable portion, as also mentioned above, the movable portion becomes bulky and needs a great space for movement. Further, such a bulky movable portion cannot move at high speed.